Hog fuel is generally sawmill refuse that has been fed through a disintegrator or hog by which the various sizes and forms are reduced to a practically uniform size of chips or shreds. Hog fuels generally contain approximately 70% to 95% bark with the residue being primarily wood.
Bark boards made without synthetic resins are known. In an Article entitled "Bark Boards Without Synthetic Resins" published by S. Chow in Volume 25, No. 11, of the Forest Products Journal, pages 32 to 37, dated November, 1975, is disclosed making bark boards without the addition of synthetic resin by forming a bark matrix into a mat and then compressing the mat in a platen press at a predetermined pressure and temperature. During the pressing step a vacuum is applied continuously to the platens to withdraw steam and water vapour. The boards were tested for dry bending strength and compared with particle board. Favourable results were obtained, however, the product has never achieved success in the marketplace.
It has now been found that by utilizing hog fuel rather than carefully selected bark, one includes at least a small percentage of wood with the bark and a percentage of wood over 5% adds additional strength to a bark board product. Inasmuch as hog fuel already has wood particles therein, it is not necessary to separate the wood particles from the bark but use the hog fuel as it comes from the hogging process to remove the bark. Furthermore, it has now been found that one can produce a hog fuel board without having to apply a vacuum to a platen press. The vacuum step is an expensive operation which may well have prevented the bark boards disclosed by Chow from being commercially feasible.
In the past hog fuel was burned, however, in today's environmental conscious environment, burning is not appropriate and therefore hog fuel accumulates in sawmills. Thus, a competitive product utilizing hog fuel provides use of what is now a waste product and solves a disposal problem.